1. Field of the Invention
The present invention relates to a belt-driving apparatus that drives a belt such as a transfer belt incorporated in an electrophotographic recording apparatus.
2. Description of the Related Art
FIG. 13 is a perspective view of a conventional belt-driving apparatus for use in an electrophotographic printer.
Referring to FIG. 13, a belt 1 is in the form of an endless belt and has a width greater than a maximum length of a printed line of an electrophotographic printer, not shown. The belt 1 is entrained about idle rollers 3, 4, and 5, and a drive roller 6, and runs at a constant speed in a direction shown by arrow C. A spring, not shown, maintains moderate tension in the belt 1 at all times. The belt 1 has an endless guide belt 2 that is attached to the inside surface of the belt 1. The guide belt 2 extends along the lateral ends portion of the belt 1 to describe a loop. The drive roller 6 has a surface made of a highly frictional material.
The idler roller 4 rotates about a shaft, not shown, on which pulleys 8 rotate freely. The pulley 8 is formed with a circumferential groove 26 therein having depth and width that are sufficient to receive the guide belt 2 therein. The groove 26 is tapered such that the groove 26 is wider at its opening than at its bottom. When the guide belt 2 is received in the groove 26, the belt 1 is ready to run properly.
The operation of the conventional belt-driving apparatus will now be described. When the drive roller 6 is driven in rotation by a drive source, not shown, the frictional force and the angle of contact between the belt 1 and the drive roller 6 cause the belt 1 to run in the direction shown by arrow C. When the belt 1 becomes skewed due to mechanical distortions of the system and variations of length of the belt 1 across the width of the belt 1, the guide belt 2 received in the groove 26 effectively alleviates the influence of the skewing problem to some extent.
However, too large an amount of skewing causes the guide belt 2 to exert a large force on the side wall of the groove 26, so that the guide belt 2 will climb the tapered side wall of the groove 26 to move out of the groove 26.
An object of the present invention is to provide a belt-driving apparatus in which the guide belt attached to an endless belt such as a transport belt is prevented from coming off the guide groove.
An object of the present invention is to provide a belt-driving apparatus in which the belt is prevented from becoming skewed.
A belt-driving apparatus has a belt in the shape of an endless loop. The belt has an outside surface and inside surface, and a guide belt that is formed on the inside surface. The belt is entrained about a roller with the inside surface in contact with the roller. The belt is entrained about the roller with a certain angle of contact. A pulley has a circumferential groove formed therein that receives the guide belt therein, and is mounted on a shaft of the roller. The pulley rotates independently of the roller. A resilient member that urges the first surface of the belt in such a direction as to increase the angle of contact. The roller may have a circumferential groove formed therein to receive the guide belt, thereby eliminating the pulley with a groove.
The resilient member is in pressure contact with the outside surface at a position between a first position and a second position to urge the outside surface of the belt toward the inside surface the belt. The first position is such that the guide belt is about to run into the groove of the pulleys and the second position is such that the guide belt has been completely received in the groove.
The resilient member may be in the shape of a plate that extends substantially parallel to an axial direction of the roller over a distance longer than a width of the belt.
The resilient member may be a cleaning blade that cleans the outside surface of the belt.
The roller, pulley, and resilient member are supported on a supporting member that may be urged by an urging member in such a direction as to maintain tension in the belt.
Instead of incorporating the pulley, the apparatus may have a groove formed in the roller. The groove may have a depth greater than a height of the guide belt such that there is a clearance between a bottom of said groove and a top of the guide belt.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.